1. Field of the Invention
The apparatus of the present invention relates to electrical power distribution systems, and more specifically to a ground fault circuit interrupter.
2. Description of the Prior Art
Ground fault circuit interrupters (GFCI) are devices which may be mounted in standard electrica- receptacle boxes and which are useful for quickly interrupting the flow of current when a fault occurs. The ground fault circuit interrupter is typically comprised of an electronic circuit for detecting the electrical fault and an electromechanical current interrupter. When the cause of the fault has been corrected, the ground fault circuit interrupter can be reset by depressing a reset button disposed on the face of the ground fault interrupter. A representative example of such a device is described in U.S. Pat. No. 3,813,579 by Doyle et al., issued on May 28, 1974.
There are several other patents which disclose ground fault circuit interrupters. The electromechanical current interrupter of these devices, however, can be characterized as an electromechanical device utilizing either a moving core and helical coil as the power element or as an electromechanical device utilizing a fixed core, helical coil and an armature as the power element. A typical example of a ground fault circuit interrupter device having a moving core which opens spring actuated contacts is disclosed in U.S. Pat. No. 4,247,840, Cooper et al., issued Jan. 21, 1981 and assigned to GTE. A typical example of a ground fault interrupter device having a fixed core which opens spring actuated contacts is disclosed in U.S. Pat. No. 4,086,549, issued Apr. 25, 1978 to assignee of the present invention.
Since the electromechanical current interrupter device of a ground fault interrupter may be disposed inside a standard electrical receptacle box, space is at a premium and it is difficult to design a reliable device having good mechanical leverage to open a pair of contacts. An approach to a similar problem is disclosed in U.S. Pat. No. 4,386,338 by Doyle et al. issued May 31, 1983 and assigned to Leviton Manufacturing Co. The apparatus of the '338 patent is similar to an impulse latching relay such as the Potter & Brimfield type PC (manufactured approximately 1955-1975) but utilizes a pulling solenoid actuation instead of a relay. The solenoid mechanism is complex and the arm opening mechanism has high friction and has a poor mechanical advantage so that a bulky coil is required to actuate the mechanism.
Accordingly, there is a need for a reliable electromechanical current interrupter device for a ground fault circuit interrupter which can directly utilize the kinetic energy of the moving core of a solenoid. The present invention, therefore, is unique among ground fault current interrupters, since it applies the operating force of the solenoid to open the contacts and does not relay upon manually set springs to perform this function.